CA1082397A

CA1082397A - Heat weldable vulcanizate comprising polyolefin rubber and propylene polymer

Info

Publication number: CA1082397A
Application number: CA251,775A
Authority: CA
Inventors: Dieter Zerpner; Klaus Zur Nedden; Albert Frese; Hans Datene
Original assignee: Chemische Werke Huels AG
Current assignee: Huels AG
Priority date: 1975-05-06
Filing date: 1976-05-04
Publication date: 1980-07-22
Also published as: IT1061236B; FR2310379B1; BE841487A; DE2520095C3; DE2520095B2; DE2520095A1; US4086301A; FR2310379A1; NL7604800A; GB1536588A; JPS51134738A

Abstract

Abstract of the Disclosure A heat-weldable vulcanised polyolefin rubber based product containing 5 to 100 parts by weight per 100 parts by weight of polyolefin rubber, of one or more propylene polymers selected from homopolymers and copolymers of propylene with up to 20% by weight of ethylene, butene-1 or hexene-1. The propylene polymer has a heptane-extractable content of 5 to 60% by weight, an I-value of 100 to 600 cm3/g and a yield stress of 10 to 30 N/mm2. The products exhibit improved weldability to each other and to conventional vulcanised polyolefin rubber products and some non-vulcanised polyolefin rubbers. :

Description

i~8Z39~7 The invention relates to heat-weldable vulcanised polyole~in rubber based products.
As is known, articles made from vulcanised polyolefin rubbers are employed in particular where high standards of resistance to weathering factors and aging factors are demanded. Thus~ for example, it is desirable in the building industry, to employ sheets of ethylene-propylene copolymers (BP~), ethylene-propylene-diene terpolymers (EPDM) or butyl rubber (BR) as a roof covering. With this type of roofing, the impermeability is very largely determined by how the joins or overlaps of the she0ts are made, 10 and these joints or overlaps present considerable problems. For this reason~ several attempts have already been made to bond articles of vulcanised polyolefin rubbers to one another or to articles made from other materials.
Thus, German Auslegeschrift 1,620,832 discloses a process for the manufacture of a firm bond between polyethylene and natural or synthetic rubber by vulcanisation using heat and pressure, characterised in that . i .
polyethylene with a melt index of less than 0.15 is used. In this process, the polyethylene is preferably applied in the form of a powder to the surface of the rubber, before applying pressure and heat. However, the ... .
polyethylene can also be employed as a sheet.
DT-OS 2,004,379 discloses the production of adhesive bonds ` `
between vulcanised layers of elastomeric copolymers and/or terpolymers o~
ethylene with an ~ -olefin, and, according to choice, a polyene and/or - butyl rubber by inserting, between these elastomeric layers, a plastomeric layer of a thermoplastic polymer and/or copolymer of ethylene, propylene ; and/or butene which is free from substituent groups having a polar character or from reactive groups, and subjecting the layers, assembled in this way, to the action of heat, preferably under pressure.
` Finally, DT-OS 2,322,594 discloses a process for bonding a shaped article of an ethylene/propylene copolymer rubber (EPM) or an ethylene/

.` ~ ' , .. . . . . . . . . .

3~823~7 propylene/diolef:in copo]ymer rubber (~PDM) to a polyole~in plastic.
~ lowever, all processes or measures of the prior art suffer from shortcomings to a greater or lesser degree. Thus, using the process of DT-OS 2,3227594 it is only possible to bond shaped articles of an ethylene/
propylene copolymer or ethylene/propylene/diene copolymer to an article of a thermoplastic material ~ a polyolefin plastic), but it is not possible to bond shaped articles of EPM or EPDM to one another.
The use of pulverulent polyolefin hot-melt adhesives according to m-os 1,620,832 suffers from the disadvantage, above all when gluing rubber roofing sheets, that the powder frequently does not remain in the place intended for welding, as a result of the slope of the roof, the wind or the hot air apparatus used for welding. For the same reason, the use of very thin film strips according to DT-OS 1,620,832 and 2,004,379 is frequently difficult. In addition, when using polyolefin film strips, four surfaces must be heated virtually uniformly, and kept in the correct position. Whilst a preliminary strip-shaped coating of the roofing sheets which are to be bonded in the areas intended for welding is possible, it is unsatisfactory ,~ :
since, in practice, deviations from the intended laying pattern cannot be avoided (due to chimneys, roof projections and the like) and this makes additional weldings necessary. When using polyolefin film strips there is furthermore the danger that when the polyolefin is melted completely, indi-vidual droplets are produced which lead to an uneven and therefore leaky weld.
It has now been found that vulcanised polyolefin rubber based products can be durably welded in a simple manner, namely solely with use of heat, if they contain 5 to 100 parts by weight per 100 parts by weight of polyolefin rubber~ of polypropylene and/or a copolymer of propylene with ~` up to 20 per cent by weight of ethyleneg butene-l or hexene-l, said propylene polymer having a heptane-extractable content of 5 to 60%, an I-value of - 100 to 600 cm3/g and a yield stress of 10 to 30 N/mm .
' ~ , ~ V8Z3g~7 :

Within the scope of the present in~ention, vulcanised products made from polyolefin rubbers are to be understood as articles, especially sheets, based on copolymers or terpolymers of ethylene with propylene and/
or butene-l~ terpolymers or quaterpolymers of ethylene and propylene and/
or butene-l witn a diene, or isobutylene--isoprene copolymers.
Preferred polyolefin rubbers ~or the manu~acture of the heat-weldable vulcanised products according to the invention are saturated polyole~in rubbers which consist of 15 to 90 per cent by weight, preferably ;;
30 to 75 per cent by weight~ of ethylene~ and of 85 to 10 per cent by weight, preferably 70 to 25 per cent by weight, of propylene and/or butene-1, and u~isaturated polyolefin rubbers which consist o ethylene and propylene and/or butene-l~ within ~he limits indicated for the saturated polyolefin rubbers, and also a polyolefin, in particular in an amount such that the rubber contains o.5 to 30 double bonds per 1,000 C atoms. Particular-ly preferred polyolefins are cis- and trans-1,4-hexadiene, dicyclopentadiene, 5-methylene-2-norbornene, 5-ethylidene-2-norbornene and 5-isopropylidene-2-norbornene. These polymers can be prepared in accordance with known processes (DT-AS 1,570,352, 1,595,442 and 1,720,450).
The butyl rubber which can be employed in the in~ention can be manufactured, for example, in accordance with the process of French Patent ~;
Specification 1,508,766.
The polypropylenes, or copolymers of propylene with up to 20 ~ `;
per cent by weight of ethylene, butene-l or hexene-l, may be obtained, for example, by polymerisation of propylene, if appropriate with ethylene and/ ~
or butene-l and/or hexene-l as comonomers~ by means of a polymerisation ~-process using a mixed catalyst consisting, on the one hand~ of a titanium-aluminium chloride of the composition TiC13 nAlC13 (n = 0.~ to o.6), such as is formed, for example, by reduction of titanium tetrachloride with aluminium metal or aluminium-organic compounds, and, on the other hand, : .. . . .

~OB~

aluminiwll-nrganic compounds. In particular, a thermally unstable titanium-aluminium chloride in the Y - or ~ -modification, which at temperatures of r up to 250 C loses the bulk of the aluminil~n chloride, may be employed.
Activation is preferably effected with diallyl-aluminium halides~ especially with dialkyl-aluminium chlorides. Below a polymerisa~ion temperature of 50C, aluminium trialkyls and aluminium dialkyl-hydrides can also be employed ; with advantage. ~urther suitable halogen-containing aluminium-organic compounds are the alkyl-aluminium sesquihalides and the alkyl-aluminium dihalides, the latter, admittedly, in combination with electron donors.
The chlorides are used preferentially. Mixtures of the different aluminium-alkyl compounds are also suitable3 for example mixtures of aluminium-trialkyls with dialkyl-aluminium chlorides.
The catalysts containing titanium trichloride are preferably . ~
employed in a concentration of 0.1 to 10 mmols/l of liquid phase, with a ~ molar ratio Al : Ti of 1 to 3 : 1, preferably 1.5 to 2.5 : 1.
.. .
~- The polymerisation may be carried out at temperatures of up to 100 C, preferably 30 to 90 C, and especially 50 to 80 C, and can be carried out either in an inert hydrocarbon known to be suitable for polymerisation ".
with the aid of Ziegler-Natta catalysts, or in the liquid monomers. Pre-; 20 ferably, the propylene is polymerised in C4-cuts which are known to contain butene-2 in addition to butane and butene-l. This is because the butene-2 accelerates the polymerisation and assists the copolymerisation of the butene-l with the propylene. Further suitable comonomers are eth~lene - and hexene-l. The addition of the comonomer or comonomers, of which up to 20 per cent by weight can be present in the polymer, lS preferably made conjointly with the propylene, since in this way copolymers with a statistical distribution of the monomer units are obtained3 such copolymers being pre-ferred.
.
- The polymerisation can be carried out continuously and dis-~ 4 continuously. ~Iydrogen can be employed to regulate the molecular weight.
The polypropylenes and copolymers of propylene with up to 20 per cent by weight of ethy~ene~ butene-l or hexene-l, which c~n be employed according to the invention, have a heptane-extractable content of 5 to 60%, preferably 8 to 45%~ an I-value of 100 to 600 cm3/g~ preferably 150 to 500 cm /g, and especially 200 to 400 cm3/g, and a yield stress of 10 to 30 N/mm , preferably 16 to 28 N/mm2~ and especially 20 to 26 N/mm . They are added to the polyolefin rubbers in an amount of 5 to 100 parts by weight, pre-ferably 15 to 60 parts by weight, relative to 100 parts by weight of poly-olefine rubber, prior to the vulcanisation.
As a rule~ the admixture can be effected without a separate process step, simultaneously with the incorporation of the additives customary in rubber technology, by means of a mill or internal mixer, and, in particular, advantageously at a temperature which is above the melting point of the polyolefin used and does not exceed 250 C, preferably 200 C.

:, ;: , The vulcanising agents are then incorpora*ed at temperatures ~ ~
which are sufficiently low that no incipient vulcanisation of the mixture ~ :
yet occurs.
Vulcanising agents which can be used are above all sulphur in combination with the known vulcanisation accelerators, with addition of zinc oxide and higher fatty acids such as~ for example, stearic acid.
Peroxides or special sulphur donors, such as, for example, N,N'-morpholine disulphide, or special thiurams may be used with equal success for cross-linking.
Additives which can be mentioned are, in the main~ active fillers and plasticisers. Possible fillers are carbon blacks of all levels of activity and the conventionally usable mineral products such a~, for example9 chalk, silicates and highly active silicas. Plasticisers which can be mentioned are the known refinery products. Amongst these, oils consisting .-: _ 5 _ , 23g~

predominantly of aromatic~ naphthen:ic or para~finic constituents can be used. In addition, all kno~n anti-aging agcnts can of co~lrs~ be added.
The subsequent carrying out of the crosslinking reaction, in presses, autoclavcs and the like, does not require any special measures.
The vulcanised products according to the invention can be heat-welded both to one another and also to conventional vulcanised polyolefin rubber based products, which do not contain the propylene polymer. The vulcanised products according to the invention can furthermore also be welded to special non-vulcanised polyolefin rubbers, and in particular to the so-called sequence polymers. This term comprises ethylene/ ~ -olefin copolymers and ethylene/ ~ -olefin/diene terpolymers which contain ethylene `~ or one of the ~ -olefins, having a statistical distribution of the monomers in the polymer chain, in the form of chain sections of different lengths.
`~ The welding, which is generally carried out on site, may be - effected~ for example, by warming the vulcanised products which are to be welded, for example products in the form of plates, profiles or sheets, in -the appropriate areas ~which are free from release agent), by means of a hot air blower to a temperature above the melting point of the polyolefin ~-~ .
;! employed, placing the warmed parts which are to be bonded in contact and ::^
- 20 pressing them together, for example by means of a pressure roller. -::. .
~- Advantageously~ the welded parts are kept under pressure until they have ., cooled to room temperature.
The Examples which follow serve further to illustrate the invention.
. ~ .
In all Examples, at least two layers are heat-welded. In prlnciple, however, ~`;. any desired number of layers can be welded. ~ `
:" :
The data given in the Examples were measured in accordance with the following methods or DIN Standard Specifications:
I-value in cm3/g: measured on an 0.1 per cent strength solution in decalin at 135 C, in accordance with m~ 53,728.

.

lOl~Z3~7 Heptane-extractable content, in %: measured by weight difference after extraction with boiling heptane.
Yield stress in N/mm = MPa: measured according to DIN 53,735.
Tear strength in N/mm : measured according to M N 53,735.
Elongation at tear in %: measured according to DIN 53,735.
Notched impact strength in KJ/m : measured according to DIN 53,453.
MFI190~5 value in g/10': measured according to DIN 53,735.
Tensile strength in N/mm : measured according to DIN 53~504.
- Elongation at break in %: measured according to DIN 53,504.
Modulus at 200% elongation in N/mm : measured according to DIN 53,504-Tear propagation resistance in N/mm: measured by the Pohle method.
Hardness at 22 C in Shore A: measured according to DIN 53,505.
Impact elasticity in %: measured according to DIN 53,512.
Peel strength in N/mm: measured according to DIN 53,274.
ample 1 `~ Pr~pa at_on of a propylene/butene-l_copolymer. ~ ;
20 parts by weight of propylene (99 per cent strength), in 50 parts by weight of a butene-2/butene-1/butane mixture, which consists of 39.2~ of trans-butene-2, 19.8% of cis-butene~2, 39.8% of n-butane, 1.0% of . c~o/~JS-~ O .
B butene-l and 0.2% of iso-butene, were to polymc~iscd at 50 C under a pressure of 10 to 7 bars by means of a mixed catalyst of 0.02 part by weight of a TiC13 ca~alyst of composition TiC13 . 0.33 AlC13 (predominantly the ~ -. , . ~
modification, commercially available aluminium-reduced titanium trichloride) :i and 0.03 part by weight of diethyl-aluminium chloride, after addition of 0.0002 part by weight of hydrogen. After a poIymerisation time of 4 hours, the polymerisation was stopped by introducing 0.1 part by weight of steam.
By spray-drying the suspension, 18.5 parts by weight of a pulverulent ~-propylene/butene-l copolymer having the following properties were obtained:
.-, .

. .

~ll08Z3~

I-va:Lue: 330 cm3/g 190/5 3-8 g/lO' Heptane extract: 11%
Yield stress: 22.3 N/mm Tear strength: 31.8 N/mm Elongation at tear:758%
Notched impact strength:
20 C 24.2 ~J/m2 0 C lO.l KJ/m -20C 5.6 KJ/m2 The copolymer was employed, together with other polypropylenes, in the experiments according to Examples 3 to 8 for testing the weldability of vulcanised products of EPDM rubber.
Example_2 M nufacture of a heat-weldable vulcanised product from EPDM rubber.
~ . .. .
A homogeneous mixture of the following components was prepared at a temperature of 180 C on a laboratory mill of size 200 x 450 mm, using a :. , .
-~ friction of 1 : 1.12:
;.' -- Parts by weight Ethylene/propylene/5-ethylidene-2-norbornene terpolYmer (BUNA ~ ~P 541) lO0 Polypropylene (I-value: 250 cm3/g;
heptane-extractable content: 42.3%;
yield stress: 20.5 N/mm2) 40 Stearic acid l Zinc oxide 5 ~
. :
Carbon black N 550 130 Siliceous chalk 30 Mineral oil 70 After cooling the mixture, the following vulcanisation system was 1~8239~7 ~

admi~ed at 50 C:
Parts by weight Sulph~ o.6 Tetramethylthiuram monosulphide 0.5 Dibenzothiazyl disulphide 1.0 Dicyelohexylammonium 0~0~-diisobutyl-dithiophosphate 1.0 Zine N-dibutyldithiocarbamate 1.0 ~ -The mixture thus obtained was then heated for 10 minutes in a vulcanisation press under 200 bars to 170 C and was pressed in a mould to give 2 mm thiek sheets, for the welding experiments. The vulcanised produet-referred to as Vulcanised Product A in Table 1 which follows, and in a part of the experiments which follow - had the following mechanical properties:
. ~
Tensile strength 13.3 N/mm Elongation at break 440 Modulus at 200% elongation 8.4 N/mm Tear propogation resistanee 23 N/mm Hardness 76 Shore A
Impaet elastieity 31%
The vulcanised produet showed no eraeks whatsoever after 7 days exposure to o7one at a concentration of 200 ppm, under 20% elongation.
Comparative Example 1 ` ~ Vulcanised Product B was prepared in accordance with the procedure ~-- of Example 2, except that the polypropylene of Example 2 was replaced by a commereially available isotactic polypropylene (I-value 400 cm3/g, practieally heptane-insoluble, yield stress 33.4 N/mm ).
..:
- Comparative Example 2 To prepare the Vuleanised Product C~ Example 2 was modified in two ways. Firstly, the roll temperature was lowered from 180 to 150 G and _ 9 _ -.: .
. - - . .
: . : . . .

8~

sccondly, instead of 40 parts by ~eight of polypropylen~ 40 parts by weight of a practically heptane-insoluble low pressure polyethylene having an I-value of 420 cm3/g was employed.
Testin~ the weldabilit~
To test the weldability, 150 mm long, 30 mm wide and 2 mm thick strips o~ Yulcanised Products A to C were welded according to DIN 53,274.
In order to obtain comparable values, the welding was carried out for 5 minutes at 170 or 140 C, not manually but in a customary vulcanisation press under 5 bars, and the peel strength was then tested at room temperature ~20 C) or at 70 C in a conventional tear tester with attached diagram recorder, at a speed of advance of 100 mm/minute. The peel strength obtained ~ -from the experiment, which is obtained from the diagram as a mean value over the peel path, is quoted in N/mm. The results are shown in Table 1.
Table 1 Vulcanised product B C
Welding temperature, C 140 170 140 170 140 170 Peel strength, N/mm (mean value over the ` peel path3 ;~ at 20 C 4-1 4-9 0.3 2.2 1.0 2.8 at 70 C 1.0 2.5 approx. approx.
. _o.o3 0-30.15 0.9 Examples 3 to 8 These Examples are intended to show the effect of changing molecular parameters of the polypropylene, or propylene copolymers, employable according to the invention (heptane-extractable content, I-value and yield stress), and the effect of the admixed amount, on the weldability. The vulcanised products were produced following the procedure of Example 2, and testing was carried out as described for Vulcanised Products A to C.
The results are shown in Table 2.

_ 10 - ~`

~0~ 3Y7 Table 2 . ._ .
Ex~mple 3 4 5 6 7 8 _ ~ ;~
Parts by weight of polypropylene~ per 100 parts by weight of EPDM 20 4o 20 40 60 40 Heptane-extractable content (%) 11 11 44 44 44 21 I-value, cm /g 330 330 230 230 230 440 Yield stress, N/mm 22.3 22.3 18.8 18.8 18.8 22.2 Peel strength, N/mm (mean value over the ~ peel ~ath) - at 22 C 3-4 4.2 5.8 5.2 4-7 4.6 at 70 C 1.5 1.9 2.6 2.0 1.7 1.5 ample 9 100 parts by weight of a saturated ethylene/propylene rubber (49% ethylene, 51% propylene~ Mooney viscosity 40) and 40 parts by weight of the polypropylene of Example 5 were mixed homogeneously at 180 C roll temperature. After the mixture had cooled, the following substances were additionally admixed~ at 50 C roll temperature:
20 Zinc oxide 7.5 parts by weight Carbon black N 774 65 " "
Mercaptobenzimidazole1 part ~' " ;

1,3-Bis-(tert,-butyl-peroxyisopropyl)-benzene3 parts " ' Triallyl cyanurate1 part " ~' The mixture thus obtained was heated for 20 minutes to 170 C in a vulcanisation press under 200 bars and was pressed to give 2 mm thick sheets for testing the weldability. The vulcanised product thus obtained had the following mechanical properties: --~ - 11 -; ~
' .~ , , -- -~- .

iV !3~3g~

Tensile strength 11.8 N/mm Elongation at break 351%
Modulus at 200% elongation 8.1 N/mm Tear propagation resistance 25 N/mm Hardness at 22 C 73 Shore A
Impact elasticity 42%
The welding~ and the peel strength test, were carried out as described for Vulcanised Products A to C. Table 3 shows the results.
Example 10 . .
O 100 parts by weight of butyl rubber (Enjay Butyl 365 sold by Esso) and 40 parts by weight of the polypropylene of Example 5 were mixed homogene-; ously at 180 C ro~Ll temperature. After cooling, the following vulcanising agents and additives were additionally admixed, at 40 C roll temperature:

Chalk 70 parts by weight Carbon Black N 550 50 ,.'!' Silicate filler (70% SiO2)15 " "
!,'` Ozokerite 5 `~ Magnesia usta, light 5 " ~' "

Stearic acid~ 1.5 " ~ ~

Zinc oxide 5 ~' " "

Sulphur 1.25 - Tetramethylthiuram disulphide 1.5 " " " ;
.. ,, ~ 2-Mercaptobenzthiazole 2.0 " ~ "

N,N'-morpholine disulphide 1.25 " " "

The mixture thus obtained was heated for 20 minutes at 150 C in ` a v~Lcanisation press under 200 bars and was pressed to give 2 mm thick sheets for testing the weldability. The vulcanised product thus obtained .. : . ~ . .
had the following mechanical properties:

Tensile strength 82 N/mm ~ ~C~c~e ~ t~ -12 -,~:

- - - .. . .. . . .

~L~8239~

Elongation at break350 Modulus at 200% elongation 64 N/mm Tear propagation resistance 18 N/mm Hardness at 22 C85 Shore A
Impact elasticity 14% - -The welding, and peel strength test~ were carried out as described ~;
for Vulcanised Products A to C. Table 3 below shows the results.
Example 11 Vulcanised Product A was welded to a vulcanised product which did not contain the polypropylene additive according to the invention and had the following composition:
Ethylene/propylene/5-ethyli~ene-2-norbornene terpolymer (~UNd~YAP 541) 100 parts by weight Stearic acid - 1 part Zinc oxide 5 parts Carbon black N 330 50 Mineral oil 10 " " "
Tetramethylthiuram disulphide1 part " ~ ;`
.:.

2-Mercaptobenzthiazole 0.5 "
, ~ . , Sulphur The welding, and peel strength test, were carried out as ~;
described for Vulcanised Products A to C. Table 3 below shows the results. ;
xample 12 .
Strips of Vulcanised Product A were welded by means of a hot air instrument having a 30 mm wide nozzle~ using a hot air temperature of about ; .
300 C, while pressing the strips together for about 1 minute with a rubber .,,~
roller. The peel strength was tested as described in detail for Vulcanised ~-,;
; Products A to C. Table 3 shows the results.
s;: , ,, ?,. - 13 - ~

;

", ~ , .
- .

39~7 ':` -- ov . ~ .', ' ' ' . c~ ~ h oo l~ ~` `
~:' ~1 ~ ~ .~
~', . _ ' ;' .; O
. ~ ~ `D
: u~ ~n ~ ~' ',.',,~,' - I ' .,~ I O I

,`i I IoO
. ~ ~
',"~' ~''' ' ~
~ . ~
': ' ~ `, `~

~ ~ R
i. ~1 h ~ V

~ ~1 I I a ~ ~ ~

; ~ 14- ~ :

. ,:
.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY ARE DEFINED AS FOLLOWS:

1. A heat-weldable vulcanised polyolefin rubber based product, which contains from 5 to 100 parts by weight per 100 parts by weight of polyolefin rubber, of at least one propylene polymer selected from homopolymers and copolymers of propylene with up to 20 per cent by weight of ethylene, butene-1 or hexene-1, said propylene polymer having a heptane-extractable content of 5 to 60% by weight, an I-value of 100 to 600 cm3/g and a yield stress of 10 to 30 N/mm2.

2. A heat-weldable vulcanised product according to claim 1, which contains as the polyolefin rubber an ethylene/propylene copolymer containing 15 to 90% by weight of ethylene and 85 to 10% by weight of propylene.

3. A heat-weldable vulcanised product according to claim 1, which contains as the polyolefin rubber an ethylene/propylene/-diene terpolymer containing 15 to 90 parts by weight of ethylene, 85 to 10 parts by weight of propylene and a diene in an amount such that the rubber contains 0.5 to 30 double bonds per 1000 C
atoms.

4. A heat-weldable vulcanised product according to claim 3, wherein the diene is 1,4-hexadiene, dicyclopentadiene, 5-methylene-2-norbornene, 5-ethylidene-2-norbornene or 5-iso-propylidene-2-norbornene.

5. A heat-weldable vulcanised product according to claim 1, which contains a butyl rubber as the polyolefin rubber.

6. A heat-weldable vulcanised product according to claim 1, 2 or 3, which contains from 15 to 60 parts by weight of the propylene polymer per 100 parts by weight of polyolefin rubber.

7. A heat-weldable vulcanised product according to claim 1, 2 or 3, wherein the propylene polymer has a heptane-extractable content of 8 to 45%, an I-value of 200 to 400 cm3/g and a yield stress of 20 to 26 N/mm2.

8. A heat-weldable product obtained by heat-welding a product as claimed in claim 1, 2 or 3.